Carburetor having a cold starting enrichment mechanism



Dec. 3, 1968 H. A. BACZKOWSKI ETAL 3,414,243

CARBURETOR HAVING A COLD STARTING ENRICHMENT MECHANISM Filed Feb. 6, 1967 NORMAL WROTTLE W/DE 64 OPEN THROTTLE l); 2 72 3"; 2 E 6 9 .56 Q 741 P .s8

. f L T; 6 5 4/9 g. L-ZfCZfOMg SK/ My l 28 $25.5 lmzaek 5 )7 IN VENT 0R5 F/cl BY m ATTORNEYS United States Patent 3,414,243 CARBURETOR HAVING A COLD STARTING ENRICHMENT MECHANISM Harry A. Baczkowski and Robert S. Harrison, Detroit,

and Charles K. Weslock, Harper Woods, Mich., assignors to Ford Motor Company, Dearborn, Mich., acorporation of Delaware Filed Feb. 6, 1967, Ser. No. 614,078 9 Claims. (Cl. 261-39) ABSTRACT OF THE DISCLOSURE A fuel conduit connects a chamber formed in the carburetor body with the fuel bowl and the carburetor induction passage posterior of the throttle blade. Positioned in the chamber adjacent the inlet of the fuel conduit is a disphragm that is urged away from the inlet but seats thereon to halt fuel flow when engine manifold vacuum exceeds a predetermined value. A control lever connected to a thermally responsive element and the throttle blade permits a spring to move the diaphragm to its seat at normal temperature and at wide open throttle only.

Summary of the invention The cold starting enrichment system used widely in present production internal combustion engines has a thermally responsive spring holding the choke plate closed when the engine is being cranked at low temperature and a piston responsive to manifold vacuum to open partially the choke plate after the engine has started. During cranking, a vacuum then exists above the throttle blade as well as below and enriching fuel is supplied through the main fuel system. It is difficult to calibrate the amount of enriching fuel supplied by such a system since any tampering with the main fuel system will affect normal engine o eration. Such systems, therefore, tend to start slowly, waste gasoline and produce large amounts of smog-producing elements. Other systems have used complicated bellows arrangements or even electrical means responsive to the current in the engine starting circuit, but these have been unsuccessful commercially because of high initial cost, the inability to prevent enriching fuel when engine operation does not require it, and poor control over the amount of enriching fuel being supplied.

This invention provides a cold starting enrichment mechanism for a carburetor that can be calibrated easily and that does not supply fuel to the engine during operation other than cold starting. In a carburetor having a carburetor body, an induction passage through the body, a throttle blade in the induction passage and a fuel source, the cold starting enrichment mechanism comprises a fuel conduit in the body leading from the fuel source to the induction passage posterior of the throttle blade. A valve member movable to a seat in response to manifold vacuum permits fuel flow through the conduit at the low manifold vacuum produced by cranking but stops fuel flow at higher vacuum.

An external member urges the valve member toward reducing fuel flow through the conduit and a control means prevents the urging member from so moving the valve member when the engine temperature is low. Enriching fuel thus flows through the conduit when the engine is being started at low temperatures but is stopped under all other conditions by the action of engine manifold vacuum or the urging member on the valve member. The amount of enriching fuel is determined by metering jets in the fuel conduit or by the location of the valve member relative to its seat.

Patented Dec. 3, 1968 ice Brie description of the drawings FIGURE 1 of the drawings is a sectioned side view of a carburetor having the cold starting enrichment mechanism of this invention showing the position of a diaphragm serving as the valve member when the engine is being started while cold. A thermally responsive element has been removed from the view. Arrows surrounding the control member indicate its movement in response to temperature and throttle opening. FIGURE 2 is an end view taken in the direction of arrow 2 in FIGURE 1 showing the thermally responsive element and additional details of the linkage connecting the control member to the throttle blade.

Detailed description As shown in FIGURE 1, a carburetor body indicated generally by the numeral 10 contains a fuel bowl 16. A cap member 18 is located on the top of body 10 where it covers bowl 16. The lower end of body 10 is shaped in the form of a flange 20 adapted for connection to an intake manifold (not shown) of an internal combustion engine by conventional means,

An induction passage 22 passes vertically through body 10 and cap 18, communicating at the top of cap 18 with the atmosphere and at the lower end of body 10 with appropriate passages in the intake manifold of the engine. Mounted by a shaft 24 near the top of induction passage 22 is a conventional choke blade 26. A throttle blade 28 is mounted on a shaft 30 in induction passage 22 posterior to choke blade 26. The portion of induction passage 22 between choke blade 26 and throttle blade 28 contains a venturi and a main fuel supply system, both of which have been removed from the drawings for clarity.

A horizontal chamber 32 is formed in body 10 adjacent induction passage 22 but separated therefrom by a wall 34. Wall 34 has a projection 36 extending a short distance into the center of chamber 32. An inlet passage 38, which is part of the enriching fuel conduit, communicates at one end with fuel bowl 16 below the fuel level and opens into chamber 32 through projection 36. Inlet passage 38 communicates through a metering jet 40 with fuel in fuel bowl 16 and through an air bleed jet 44 with the air and fuel vapors above the fuel.

Making up the remainder of the enriching fuel conduit is an outlet passage 46 opening at one end into the annulus of chamber 32 surrounding projection 36 and at its other end into induction passage 22 posterior of throttle blade 28.

Attached to the wall of chamber 32 is a flexible diaphragm 48, the valve member. Diaphragm 48 is positioned adjacent the opening of inlet passage 38 into chamber 32 and projection 36 forms a seat 49 for diaphragm 48 around the opening of inlet passage 38. A spring 50 seats in the annulus of chamber 32 surrounding projection 36 and urges diaphragm 48 away from the seat 49. Slidably positioned in chamber 32 on the other side of diaphragm 48 is a cam 52. A snap ring 54 located in the end of chamber 32 holds cam 52 inside chamber 32 but does not interfere with a projection 53 of cam 52 extending outside of the walls forming chamber 32.

A pivot pin 56 is located near the outside lower end of chamber 32 and has mounted thereon a coil spring 58 and a lever 60. Coil spring 58 has one tang bearing on the wall forming chamber 32 and the other tang urging lever 60 into touch with projection 53. The relationship of pin 56, spring 58, and lever 60 is pictured best in FIGURE 2 where it is seen that lever 60 has two legs pivoting on pin 56 with spring 58 mounted between the legs. Lever 60 is the external member urging the valve member toward reducing fuel flow through the fuel conduit.

The control means of the invention comprises a control lever 62. Lever 62 is fastened to a shaft 64 that is mounted pivotally in carburetor body above chamber 32. At its lower end, control lever 62 contacts the upper end of spring-loaded lever 60. The upper end of control lever 62 projects outboard where it is connected to a link 66. Link 66 rides in a slot 68 (see FIGURE 2) formed in one side of an intermediate lever 70. A portion of lever 70 is broken away in FIGURE 2 to show the structure of pin 56, spring 58 and lever 60. Lever 70 pivots on a shaft 72 that is attached to carburetor body 10.

Throttle blade shaft 30 projects from carburetor body 10 adjacent intermediate lever 70 and has mounted thereon a throttle lever 74. Throttle lever 74 is outboard of intermediate lever 70 and shaft 72 but has an upper tang 76 and a lower tang 78 projecting inward toward lever 70. Upper tang 76 threadably engages a threaded member 80 bearing on a cam surface 82 (see FIGURE 2) of intermediate lever 70 while lower tang 78 terminates adjacent a step 84 formed on lever 70.

Referring to FIGURE 2, a thermally responsive element 86 is mounted in a housing 88 attached to carburetor body 10 by conventional means (not shown). Shaft 64 projects into housing 88 where it is attached to a lever 90 that in turn is attached to thermally responsive element 86.

Operation When the engine is at a temperature requiring cold starting enrichment fuel, thermally responsive element 86 acts through lever 90 to rotate shaft 64 and lever 62 in a clockwise direction in FIGURE 1. The lower end of lever 62 then contacts lever 60 to pivot lever 60 counterclockwise about pivot pin 56 and thereby remove the effect of spring 58 on diaphragm 48. Engine cranking produces a vacuum in induction passage 22 posterior to throttle blade 28 sufficient to draw enriching fuel through passages 38 and 46 but insuflicient to draw diaphragm 48 onto seat 49. Enriching fuel then is supplied to the engine via passages 38 and 46. When the engine starts, the manifold vacuum applied through passage 46 draws diaphragm 48 onto seat 49 to stop the enriching fuel.

If throttle blade 28 is opened to a position near wide open throttle to accelerate while the engine is cold, the manifold vacuum in passage 46 drops to a low value and diaphragm 48 tends to move off seat 49. Unnecessary enriching fuel then could flow through passages 38 and 46 but this is prevented through the following operation of control lever 62 and spring loaded lever 60.

Lever 74 pivots counterclockwise in FIGURE 2 when moving throttle blade 28 toward the wide open throttle position. As throttle blade 28 nears the wide open throttle position tang 78 of lever 74 contacts step 84 of lever 70, thereby pivoting lever 70 in a clockwise direction. Link 66 then pivots control lever 62 counterclockwise in FIG- URE 1 to move lever 62 out of touch with spring loaded lever 60. Spring loaded lever 60 then applies the force of spring 58 through cam 52 to diaphragm 48, thereby holding diaphragm 48 on seat 49 to prevent the enriching fuel from passing through passages 38 and 46.

When the engine is at a temperature not requiring enriching fuel for starting, thermally responsive element 86 acts through lever 90 to pivot shaft 64 and lever 62 in a counterclockwise direction in FIGURE 1. Lever 62 then is out of touch with spring loaded lever 60 and the force of spring 58 acting through lever 60 and cam 52 maintains diaphragm 48 on seat 49 regardless of the manifold vacuum appearing in passage 46. Enriching fuel thus is prevented from flowing through passages 38 and 46.

The amount of enriching fuel supplied to the engine through passages 38 and 46 is adjusted to engine require ments by selecting appropriate metering jets 40 and 44 or by appropriately positioning diaphragm 48 relative to seat 49. If desired, thermally responsive element 86 can be used to position choke blade 26 for proper cold operation by appropriate linkage.

Thus this invention provides a cold starting enrichment mechanism that meters proper amounts of enriching fuel when required by the engine and prevents that enriching fuel from reaching the engine for all other engine operating conditions. The amount of enriching fuel can be matched accurately to engine requirements and the enriching mechanism can be used in venturi or air valve carburetors.

What is claimed is:

1. In a carburetor for an internal combustion engine having a carburetor body, an induction passage through said body, a throttle blade in said passage and a fuel source; a cold starting enrichment mechanism comprising a fuel conduit in the body leading from the fuel source to the induction passage posterior of the throttle blade,

a valve member movable in response to manifold vacuum to control the fuel flow through said conduit,

means urging said valve member toward reducing fuel flow through the conduit, said means including a cam movable into contact with the valve member and a spring loaded lever urging said cam toward the valve member and,

control means preventing the urging means from moving the valve member to reduce fuel flow through the conduit when the temperature is low.

2. The carburetor of claim 1 in which the control means comprises a thermally responsive element connected to a control lever, said control lever preventing said spring loaded lever from moving said valve member when the temperature is low.

3. The carburetor of claim 2 in which the control lever is connected to the throttle blade, said control lever permitting said spring loaded lever to move said valve member when the throttle blade is near its wide open position.

4. The carburetor of claim 3 in which the valve member comprises a flexible diaphragm positioned in a chamber in the carburetor body, and

the fuel conduit comprises an inlet passage from the fuel source opening into said chamber adjacent the central portion of said diaphragm and an outlet passage leading from said chamber to the induction passage, the opening of the inlet passage into said chamber forming a seat for the diaphragm.

5. The carburetor of claim 4 in which the flexible diaphragm is spring loaded away from the seat but is movable to said seat when the manifold vacuum applied to the chamber via the outlet passage exceeds a predetermined minimum.

6. The carburetor of claim 1 in which the control means is linked to the throttle blade so the control means permits the urging means to move the valve member to reduce fuel flow through the fuel conduit when the throttle blade is near its wide open position.

7. The carburetor of claim 1 in which the valve member comprises a flexible diaphragm positioned in a chamber in the carburetor body and the fuel conduit comprises an inlet passage from the fuel source opening into said chamber adjacent the central portion of the diaphragm and an outlet passage leading from said chamber to the induction passage, the opening of the inlet passage into said chamber forming a seat for the diaphragm.

8. In a carburetor for an internal combustion engine having a carburetor body, an induction passage through said body, a throttle blade in said passage and a fuel source; a cold starting enrichment mechanism comprising a chamber located in the carburetor body,

a diaphragm located in said chamber,

a fuel conduit in the carburetor body comprising an inlet passage leading from the fuel source to the chamber and an outlet passage leading from the chamber to the induction passage posterior of the throttle blade, the opening of the inlet passage into the chamber forming a seat for the diaphragm, spring means urging said diaphragm away from the seat but permitting the diaphragm to reach the seat when the vacuum in the induction passage posterior of the throttle blade reaches a predetermined value, spring loaded means urging the diaphragm toward the seat and control means preventing said spring loaded means from moving the diaphragm to its seat when engine temperature is low. 9. The carburetor of claim 8 in which the control means comprises a control lever connected to the throttle valve to permit the spring loaded means to move the diaphragm to its seat when the throttle blade is near its wide open position.

References Cited UNITED STATES PATENTS Sarto 261-39 Wise 261-39 Sarto 261-39 Gast 261-39 Carlson 261-39 Bickhaus et a1. 261-39 Thomas 261-39 HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Assistant Examiner. 

